Tk-2 large water pressure drop

**sapo** · 02-01-2013, 02:36 PM

Hi, so i finally got the remote for my T-K2. It does not show any trouble codes

Any one have any other suggestions?
I was thinking it must be a non sensor issue since it gets no codes. Perhaps the control valve is acting on it's own.
Any help would be great.

**lifespeed** · 02-01-2013, 02:47 PM

Originally Posted by sapo

Hi, so i finally got the remote for my T-K2. It does not show any trouble codes

Any one have any other suggestions?
I was thinking it must be a non sensor issue since it gets no codes. Perhaps the control valve is acting on it's own.
Any help would be great.

Did you ever measure the temperature of the hot water and compare it to the setpoint? You already know the heater is shutting down the flow rate, now you have to figure out why. If the temp is correct then perhaps it is incapable of putting out enough BTU, so it throttles the water flow to maintain temp.

If you can't do the troubleshooting you're going to have to hire somebody who can, or buy a new heater.

**sapo** · 02-02-2013, 07:42 AM

I checked the output temp with a thermometer at the faucet. It is the correct temp. The new remote also verified the set point and output temp as being accurate.
When the problem started back in october the incoming water temp was warmer than it is now, yet the output temp and gpm has remained the same. This would suggest to me that the burner capacity is not taxed.
I emailed the company, i guess i'll see what they have to say.
At this point my wallet prevents me from hireing someone or buying a new unit.
The control valve is only $90 so i might throw a new one at it and see if it sticks.

**lifespeed** · 02-02-2013, 10:41 AM

Originally Posted by sapo

. . . yet the output temp and gpm has remained the same. This would suggest to me that the burner capacity is not taxed.
I emailed the company, i guess i'll see what they have to say.

Most tankless heaters will reduce the output flow, using their flow control valve, in order to maintain water temperature. Given your problem (reduced flow rate when the heater is plugged in and controlling output flow), it would appear that your burner is not being asked to produce maximum rated BTU. There is a possibility it is not capable of max BTU output, so the water heater throttles the flow to maintain temperature. So maybe a problem on the burner side, or it's gas valve and control.

There is also the possibility your flow control valve won't open up all the way, so the brain throttles back the gas to avoid overtemp. But you said when unplugged the flow control valve opens up, right? So not a mechanical blockage, but possibly electrical control and or the servo within the valve itself?

Talk to Takagi and see if there is a diagnostic mode available, where you can manually command the flow valve. You need to identify if the problem lies in the water control side, or the flame control side. Either one could potentially cut down your water flow.

Unfortunately these water heaters are somewhat more complicated. Hopefully they have provided some helpful built-in diagnostics and manual controls to allow you to determine the problem without guessing and parts-swapping too much.

Edit: Here's a test - turn the temperature up all the way, hopefully it will allow you to go up to 140F or so. See if the water flow rate is reduced. Then turn the temperature down to 110F. See if the water flow increases. This should tell you if the heater is limiting water flow based on limited burning capacity.